Artificial Recharge of Groundwater with Stormwater as a New Water Resource - Case Study of the Gaza Strip, Palestine

Due to the existing deficit in the water resources budget in the Gaza Strip, the groundwater quality was deteriorated and salinity reached more than 1500 mg/l as chloride ion. Moreover the groundwater level declined continuously until it reached few meters below sea levels in most areas. Non-conventional water resources such as desalination, wastewater reuse and storm water harvesting are needed to bridge the gab in water resources budget in the Gaza Strip, Palestine. Desalination is faced by fiDue to the existing deficit in the water resources budget in the Gaza Strip, the groundwater quality was deteriorated and salinity reached more than 1500 mg/l as chloride ion. Moreover the groundwater level declined continuously until it reached few meters below sea levels in most areas. Non-conventional water resources such as desalination, wastewater reuse and storm water harvesting are needed to bridge the gab in water resources budget in the Gaza Strip, Palestine. Desalination is faced by financial constraints in addition to problems of available power. Wastewater reuse and artificial recharge with effluent is still at early stages since the quality of the effluent does not meet the local nor international standards for either direct reuse for irrigation and artificial recharge of the aquifer. Urban stormwater harvesting became an important water resource that plays a significant role in enhancement of water resources management. It has a potential input of about 28 Mm3 per year as runoff, from which 22 Mm3 come from urban areas in cities only based on the existing landuse. Collection of storm water running from rooftops and yards of buildings and diverting it into local onsite artificial infiltration systems will decrease the road flooding and water quantities reached the central rainwater collection lagoons. Since the people are well aware of the severe water problem, they are willing to adopt this technique in the form of onsite rooftop rainwater infiltration at their houses. However, financial incentives are needed from the local authorities to make this option successful. Using GIS, it was estimated that the total rainwater harvested from house roofs and open yards belong to buildings was 5.2 Mm3, which forms 24% of the whole urban storm water in the Gaza Strip. Onsite RWH was tested at one pilot concrete house located at the middle of the Gaza Strip, and the collected water quantity and quality were monitored in the rainy season. Quantitatively, it was found that rain runoff coefficient from roofs and yards increases with the increase of rainfall intensity and rainstorm duration. The runoff coefficient reached more than 0.9 for high intensity rain events and 0.4 for low intensity ones. The harvested rooftop stormwater runoff in Gaza has proved to be suitable for artificial recharge and close to WHO drinking water standards, where low concentrations of chloride and nitrate were found. The measured concentrations of lead, cadmium, iron, zinc, chromium, aluminum and copper were in the acceptable limits set by WHO for drinking purposes. However, relatively high concentrations of total organic carbon (TOC) were found in urban road runoff water. The concentrations of poisonous metals, such as cadmium and lead, were found to be close to the international, regional and local standards for artificial recharge purposes. There is no danger from the mobility of these metals in the infiltrating water, since pH values of all measured samples were close to7.0, under which most of the heavy metals will be absorbed, precipitated or co-precipitated in the soil aquifer matrix through its infiltration to the groundwater.…